Thomas;
I had the same experience with a new MAC Powerbook laptop, also running MS XP on one side ( which is very hard to find these days ). I use AVG on the PC side of the HD but I don't recall any issues with the firewall or antivirus.
In my case, I took the old version of Beoplayer off ( using Add/Remove ), rebooted, reinstalled the new version of Beoplayer off the B&O website, rebooted, and then re-registered. . I lost no music, photos, or video files, as I use the XP Media Centre version, and load those items first via Mediaplayer. The new Beoplayer simply scanned and loaded everything including the icons from those files.
The MAC is a great laptop, with some fantastic programs, but I enjoy Beoplayer music and radio through our main PC / ML Beosystem, and keep it consistent with the MAC.
Let us know, as I hope this is helpful and successful for you.